Calculations

Question 1

Define Mole

Answer 1

The mole is the amount of substance in grams that has the same number of particles as there are atoms in 12 grams of carbon 12.

Question 2

Define Relative atomic mass.

Answer 2

Relative atomic mass is the average mass of one atom compared to one twelfth of the mass of one atom of carbon-12

Question 3

Define Relative molecular mass

Answer 3

Relrative molecular mass is the average mass of a molecule compared to one twelfth of the mass of one atom of carbon-12

Question 4

State the equation for moles in solids, liquids and gases.

Answer 4

Moles = mass / mr, Always quote mr to 1dp.

Question 5

State the Ideal gas equation.

Answer 5

PV = nRT
P (pa)
V (m3, L)
n (mols)
R (constant)
T(K)

Question 6

State the equation for moles in solution.

Answer 6

moles = conc * vol

Question 7

Calculate the mass of 1 atom of Cupper 64

Answer 7

64 / 6.022E23 = 1.0627698e-22

Question 8

Calculate how many atoms in 6g of tin metal.

Answer 8

6 / 118.7 = 0.05055

0.05055 * 6.022E23 =3.04E22

Question 9

State the equation for density.

Answer 9

D = m / v

Question 10

Define empirical formula

Answer 10

An empirical formula is thesimplestratio of atoms of eachelementin the compound

Question 11

State the step in determining the empirical formula.

Answer 11

Step 1 : Divide each mass (or % mass) by the atomic mass of the element
Step 2 : For each of the answers from step 1 divide by the smallest one of thosenumbers.
Step 3: sometimes the numbers calculated in step 2 will need to be multiplied up togive whole numbers.
These whole numbers will be the empiricalformula.

Question 12

Define Molecular formula

Answer 12

A molecular formula is theactualnumber of atoms of each element in the compound